For a proper development shop, the developers wouldn't use the generated code. It would require so much rework to fit their framework that you might as well just write it from scratch. I have worked with tools like yours, Adobe has an enterprise product that is a bit ahead of yours.

Writing HTML and CSS is not the hard part of front-end development. A modest developer can put this together quickly. The hard part is using javascript or someone other tech to piece it all together.

I would encourage you not to chase your internal goal. Instead, focus on making designers better instead of trying to turn designers into developers. W3C will release a new CSS/HTML spec, or some fancy new JS framework will come out and you'll be left scrambling to re-engineer.